On the stability of a coupled ocean atmosphere system in the presence of wave-CISK

The stability of a simple coupled ocean-atmosphere system similar to the one studied by Hirst with general ocean thermodynamics is investigated in which the atmospheric heating is determined by sea surface temperature anomalies as well as the convergence feedback (low level moisture convergence by the waves themselves). It is shown that the unstable coupled mode found by Hirst (UH mode) is profoundly modified by the convergence feedback. The feedback increases the unstable range of the UH mode and can increase its growth rate several folds. The maximally growing UH mode can become westward propagating for certain strength of convergence feedback. If the convergence feedback strength exceeds a critical value, several new unstable intraseasonal modes are also introduced. These modes are basically ‘advective’ modes. For relatively weak strengths of the convergence feedback the growth rates of these modes are smaller than that of the UH mode. As the atmosphere approaches ‘moist neutral’ state, the growth rates of these modes could become comparable or even larger than that of the UH mode. It is argued that these results explain why the El Nino and Southern Oscillation (ENSO) signal is clear in the eastern Pacific but not so in the western Pacific and they may also explain some of the differences between individual ENSO events. Our results also explain the aperiodic behaviour of some coupled numerical models. Importance of this process in explaining the observed aperiodicity of the ENSO phenomenon is indicated.     

Integrated surface–groundwater flow modeling: A free-surface overland flow boundary condition in a parallel groundwater flow model

Interactions between surface and groundwater are a key component of the hydrologic budget on the watershed scale. Models that honor these interactions are commonly based on the conductance concept that presumes a distinct interface at the land surface, separating the surface from the subsurface domain. These types of models link the subsurface and surface domains via an exchange flux that depends upon the magnitude and direction of the hydraulic gradient across the interface and a proportionality constant (a measure of the hydraulic connectivity). Because experimental evidence of such a distinct interface is often lacking in field systems, there is a need for a more general coupled modeling approach.     

面向对象时空数据模型的研究

时空数据模型是建立TGIS的基础.首先指出了建立时空数据模型中应该考虑的问题,同时指出面向对象时空数据模型的优越性;然后提出了面向对象的时空数据模型.指出地理世界抽象是由时空属性对象组成,每个时空属性对象由空间、属性、时间3部分组成.系统分析了时空属性对象各个组成部分之间的关系并通过UML进行了表达.最后,以地籍管理中的宗地为例说明了该数据模型的实现.     

Galvanic interactions between galena–sphalerite and their reactivity

The galvanic effect between the main associated mineralogical phases in a mineral sphalerite concentrate was evaluated using an alternative methodology. Comparative voltammetric studies were performed between high purity galena mineral (94.65%) and sphalerite concentrate (content of 78.11% sphalerite, ZnS; 13.64% galena, PbS; 0.57% chalcopyrite, CuFeS₂; 0.41% cadmium sulfide, CdS; and 0.11% arsenopyrite, FeAsS) using carbon paste electrodes (CPE) in order to identify galvanic interactions that affect their reactivity. The electrolyte was an aqueous solution of 0.1 M NaNO₃ (pH 6.5). The results showed that, in sphalerite concentrate, the electrochemical reactivity of the galena was diminished and displaced to more positive potentials with respect to the high purity galena mineral response. This behavior can be attributed to the galvanic protection offered by the sphalerite on the galena, thereby avoiding its free oxidation. On the other hand, sphalerite oxidation was diminished by the formation of a passive products film that is dissolved to more positive potentials which provokes oxidation of other minerals like CuFeS₂, (Zn,Cd)S and FeAsS present in a minor proportion in the sphalerite concentrate.     

Addressing Hurricane Intensity through Angular Momentum and Scale Energetics Approaches

This paper addresses two avenues for gaining insight into the hurricane intensity issue—the angular momentum approach and the scale interaction approach. In the angular momentum framework, the torques acting on a parcel's angular momentum are considered along an inflowing trajectory in order to construct the angular momentum budget. These torques are separable into three components: The pressure torque, the surface friction torque, and the cloud torque. All torques are found to diminish the angular momentum of an inflowing parcel, with the cloud torques having the most important role. In the scale interaction approach, energy exchanges among different scales within a hurricane are considered as a means of understanding hurricane intensity. It is found that the majority of kinetic energy contribution to the hurricane scales originates from potential-to-kinetic in-scale energy conversions. The contribution of mean-wave interactions in the kinetic energy varies with distance from the center and with the life stage of a storm. In the early stages, as the disorganized convection becomes organized on the hurricane scales, upscale energy transfers (i.e., from small to large scale) are found to take place in the outer radii of the storm. In a mature storm, the kinetic energy transfers are downscale, except for the inner radii.     

近46年辽宁省降水集中程度研究

利用辽宁省25个台站1960—2005年逐候的降水资料，运用降水集中度和集中期分别讨论了辽宁省降水时空分布特征和变化规律，同时对多水年和少水年的集中度进行了比较。结果表明降水集中度和集中期能够定量地表征降水量在时空场上的非均一性，降水集中度平均为0．655，最大为0．749，最小为0．509；集中期平均为40．953候，最大值为45．221候，最小值为37．697候。年降水集中度和汛期降水集中度均呈减小趋势，汛期降水集中度减小的趋势明显。降水集中度的EOF分析显示取前3个特征值对应的特征向量可解释70％以上的方差。第一特征向量表现为全省一致性，而第二特征向量表征为东南与西北地区的反相，第三特征向量表征为东部山区与西部和沿海地区的反相。多水年的降水集中度明显比少水年的偏大且多水年的降水集中度分布较少水年复杂。     

The spatial structure of the dayside ionospheric trough

Tomographic imaging provides a powerful technique for obtaining images of the spatial distribution of ionospheric electron density at polar latitudes. The method, which involves monitoring radio transmissions from the Navy Navigation Satellite System at a meridional chain of ground receivers, has particular potential for complementing temporal measurements by other observing techniques such as the EISCAT incoherent-scatter radar facility. Tomographic reconstructions are presented here from a two-week campaign in November 1995 that show large-scale structuring of the polar ionosphere. Measurements by the EISCAT radar confirm the authenticity of the technique and provide additional information of the plasma electron and ion temperatures. The dayside trough, persistently observed at high latitudes during a geomagnetically quiet period but migrating to lower latitudes with increasing activity, is discussed in relationship to the pattern of the polarcap convection.     

Geophysical phenomena during an ionospheric modification experiment at Tromsø, Norway

We present an analysis of phenomena observed by HF distance-diagnostic tools located in St. Petersburg combined with multi-instrument observation at Tromsø in the HF modified ionosphere during a magnetospheric substorm. The observed phenomena that occurred during the Tromsø heating experiment in the nightside auroral E_s region of the ionosphere depend on the phase of substorm. The heating excited small-scale field-aligned irregularities in the E region responsible for field-aligned scattering of diagnostic HF waves. The equipment used in the experiment was sensitive to electron density irregularities with wavelengths 12–15 m across the geomagnetic field lines. Analysis of the Doppler measurement data shows the appearance of quasiperiodic variations with a Doppler frequency shift, f_d and periods about 100–120 s during the heating cycle coinciding in time with the first substorm activation and initiation of the upward field-aligned currents. A relationship between wave variations in f_d and magnetic pulsations in the Y-component of the geomagnetic field at Tromsø was detected. The analysis of the magnetic field variations from the IMAGE magnetometer stations shows that ULF waves occurred, not only at Tromsø, but in the adjacent area bounded by geographical latitudes from 70.5° to 68° and longitudes from 16° to 27°. It is suggested that the ULF observed can result from superposition of the natural and heater-induced ULF waves. During the substorm expansion a strong stimulated electromagnetic emission (SEE) at the third harmonic of the downshifted maximum frequency was found. It is believed that SEE is accompanied by excitation of the VLF waves penetrating into magneto-sphere and stimulating the precipitation of the energetic electrons (10–40 keV) of about 1-min duration. This is due to a cyclotron resonant interaction of natural precipitating electrons (1–10 keV) with heater-induced whistler waves in the magnetosphere. It is reasonable to suppose that a new substorm activation, exactly above Tromsø, was closely connected with the heater-induced precipitation of energetic electrons.     

A statistical study of field-aligned electron beams associated with ion conies events

A statistical study of field-aligned electron beams associated with upflowing ion conics is presented from Exos-D (Akebono) observations below 10 000 km. The electron beams are narrowly collimated along the field line and generally have energies of several tens of eV. They are divided in the analysis into three types: upflowing, downflowing, and counterstreaming. All the types of electron beams are almost equivalent in their energy and pitch angle characteristics and their association rate with upflowing ion events. About 50% of ion conies are found to be coincident with field-aligned electron beams. There is also a correlation in energy between the field-aligned electrons and ion conics. These show that the association is not a mere coincidence but rather that the field-aligned acceleration of electrons is related to the perpendicular energization of ions. The association rate of upflowing electrons is high on the nightside, while that of downflowing electrons is high on the dayside. The association rate of downflowing electrons is high at low altitudes, and the rates of the three types of electron beams become equivalent at high altitudes. Data indicate that the height of the electron acceleration region is lower on the nightside. It is suggested that the average height of the electron acceleration region is around the satellite apogee (–10000 km), and the average thickness of the region is about thousands km.